Process for the gasification of fine grained or pulverulent fuels



l k April 9, 1957 P. scHMALFELD Erm. 2,788,314 `PRocFss Foa THE cAsIFIcATIoN oF FINE GRAINED OR PULVERULENT FUELS Filed July 22, 1950 vf5 i fag,N 1

United States l PROCESS FOR THE GASlFICATI-ION F FINE GRAINED OR` PULVERULENT FUELS Appiication uly 22, 1950, Serial No. 175,344 4"Claims priority, application Germany August 3, 1949 11 Claims. (Cl. 202-14) AThis invention relates to a process for the degaslftcation of fine-grained or pulverulent fuels or the like.

It is known to heat pulverulent fuels in externally heated retorts in the absence of air, for the purpose of tcoking said fuels, while recovering gas, tar and coke. The fuels may be quiescent in the retorts, or they may fbe moved in or through the retorts mechanically or by itheir own gravity or by a carrier gas. lt is also known tto iheat and coke pulverulent fuels directly by means of vhot gases, either in suspension or in a loose mass agitated Eby the hot gas (fluidised bed). Direct heating of fine- ;grained fuels for degasication has also been carried out :by means of line-grained solid heat carriers. Thus, fine oil shale has been blown into a retort by means of steam `along with heated tine shale residue, and has been mainttained in the retort, by `the steam in an agitated mass f-(uidised bed). The line shale residue heated in a sep- :arate chamber supplies `the heat Vfor degasication (E. V. iMnrphree, Gas, Coal, Oil Shale, The Oil and Gas journal of 8. 4. 1948, p.. 69),.

All these known processes suffer from certain dis- :aiivantages which, in the case of quiescent disposition ofthe pulverulent fuel to 4be treated, lreside in an in- :adequate specic ciiciency and in the case of material 5in motion, in the considerable entraininent of dust into fthe outgoing degasitication gas, and also in the dilutio sof the degasification gas, by the carrier gas.

XA process has also been proposed in which a coarsegrained or lumpy solid heat carrier supplies the heat for tdegasication. In this case, `the heat carrier, after being lheated in a separate chamber, is mixed with the finegrained fuel and conveyed through a lrotary drum which :acts as a degasiiication chamber. The process was used or `degasifying caking coal for the production of pre- :dominantly iine coke. After separation of the coke, the :heat carrier was elevated, heated up and returned for idegasification (Adolf Thau, Die Schwelung von Braun ,und Steinkol'1le-The low-temperature carbonisation of Zbrown coal and pit coa1-Halle, 1927, pp. 685 et seq.).

This process requires a considerable number of mefchanical devices and has an unfavourable heat exchange tbetween heat carrier and the fuel to be degasied,

The process according to the invention operates with nine-grained or pulverulent solid heat carriers, utilises ttheir favourable heat transfer in the degasication of inne-grained or pulverulent fuels or the like and neverthe- .less results in a degasitcation gas which is substantially 'free from dust.

IAccording to the present invention, the heated fine- ;gra'ined or pulverulent heat carriers, together' with fineigrained or pulverulent fuels or the like, are passed, pref- =erably by their own weight, `in the form of a substantially "closed downwardly moving charge, through the degasication chamber in such a manner that, at the degasilica ftion zone, a free surface ofthe charge `is formed or jprovision is made in vsame other `way for undisturbed' escapeV of the` gas Vfrom fthe v charge.

l arent ice The expression passing a substantially closed charge through the chamber means a movement of the material of the charge in such a manner that the particles of the material follow each other without essential interstices or that the particles touch each other. The expression free surface or such similar term as used herein is intended to include a large single free surface such as an open top surface or surface of banked material as well as the aggregate of multiple relatively small individual free surfaces such as may be established by the apertures of screens, sieves, or perforated elements. of conventional type.

Fuel and heat carrier are preferably mixed` together before or at the entry into the degasiiication chamber. Due to the intimate contact of the dust to be degasied with the hot heat carrier, the dust or pulverulent fuel is rapidly heated and gives ofI its volatile constituents, gas, tar and distillation liquor, according to the temperature to which it is heated.

Since there is no need to use any carrier gas in the process o f the present invention, the degasication gas is able to leave the charge undiluted.. The smaller quantity of gas permits a lower gas velocity, which prevents or diminishes the blowing up of the charge at the points of escape. A further safe guard against the en-r trainment of dust by the gas formed during degasication may be attained by making the escape surfaces-,of the gas from the downwardly moving fuel charge correspondingly large. These escape surfaces may be formed for example by `providing free bank surfaces of the charge, or by using louvres, sieves, gratings or the like as retaining walls for the descending charge of `fueland heat carrier. The degasication gas may then be collected in a gas chamber without entrainrnent of dust and led away, for example, to a cooling, condensation and scrubbing apparatus. The intimate contact of the dust or powder with the hot heat carrier results in a high specic efficiency of the apparatus.

In the herein described process, for example, a `finegrained or pulverulent heat carrier is used which, with suitable material to be degasiied, conveniently consists of the coke or residues formed in the degasication., After withdrawal from the degasification chamber Athe mixture of circulating heat carrier and newly formed coke or residue, which is likewise used in ne-grained `or pulverulent form, is elevated pneumatically by means of air and if desired with the addition of other gases, with simultaneous heating, preferably by the reaction of the conveying air with carbon contained in the residue.

Depending upon temperature conditions and reaction velocities, the reaction results in varying ratios of carbon dioxide to carbon monoxide in the reaction gases `of the conveying air.

The heat carrier, after being heated up, is separated in a separator from the reaction gases of the conveying air and is returned to the degasilication chamber. Advantageously, the separator is one primarily for coarse particles for example in the form of a settling chamber or a simple cyclone, so that the nest fractions are separated `only to a limited extent and are led out of the heat carrier circuit together with Athe reaction gases.

' If vthe coke produced or its ash does not possess an adequate granular form, i. e. if it is for example, too line, it is possible to employ asheat carrier, for example, other fuel ashes, chamotte, alumina, silica (quartz or other modifications), silicates, magnesium oxides or the like, or mixtures thereof. The heat carrier should preferably not tend to deteriorate excessively such as by splintering, abrasion, chemical reaction or'the like, so that the amount requiredtand the production of'tine dust will notin'crease excessively. It ydesired `it ispossibleto use an extraneous heat carrier in addition to the residue of the degasication i material.

The grain of the circulation heat carrier preferably lies between about 0.1 and 1.0 mm. diameter. If the grain isner than 0.1 mm. separation from the conveying gases is generally more difiicult and requires separators for fines operating at a higher gas velocity and hence with a higher power consumption due to the necessarily encurred pressure loss. vOn the other hand, the velocity necessary for maintaining suspension increases with the grain diameter, so that the velocities required for the pneumatic conveying and hence the power consumption and deterioration increase with the grain diameter', and at Isubstantially greater diameters than 1.0 mm. the costs of theprocess may increase 'to' render the same uneconomical.

Preferably, the fuel introduced has likewise a maximum grain size of 1.0 mm. It may, however, also be somewhat coarser, since shrinkage or diminution of the specific gravity ofthe grain occurs through the degasification process. The advantageous grain size of the fuel can readily be attained by screening, or if coarse grain is supplied, it can readily be produced by simple pulverising, and does not require any high grinding costs, such as is frequently the case in normal pulverised fuel tiring or dust gasification, owing to the requirement for a very finely ground powder. The circulation of the heat carrier is regulated so that the latter, together with the material to be degasfied, moves in a closed charge through the degasification charnber, the latter being closed from the conveyer chamber land separation chamber preferably by the charge. 'This is achieved, for example, by providing below the degasification chamber, a throttle device which allows to adjust the quantity of the mixture of heat carrier and residue leaving the degasification chamber. In particular, if care is taken to ensure that the mixture of heat carrier and degasification material is introduced into the degasication chamber in a closed charge, a further result of the throttling is that there is a closed column of material in the degasification chamber. The height of the column of material is determined, for example, by an overflow, through which excess of heat carrier is removed before `the supply of fresh material to be degasifed enters. On its passage through the degasification chamber, the heat carrier is increased by the degasification residue.

After pneumatic conveying, the most finely granular fraction is partly separated. The heated heat carrier, together with the freshly supplied fuel, then forms the charge and the excess flows away through the overflow. If no excess remains, because the proportions of fine dust being removed is greater than the supply of degasification residue, additional heat carrier is preferably introduced into the cycle so as to maintain a closed charge. This may be effected, for example, together with the material to be degasified. The closed column of material from the throttle device to the overflow prevents flow of gas between the gas chamber of the degasication chamber on the one hand and the conveyor charnber or separation chamber on the other. Preferably, the pressure in the degasification chamber is maintained in constant dependence upon the pressure in the pneumatic conveying chamber. E. g. there should be maintained in the separation chamber of the separator a suitable excess pressure relative to the pressure in the degasication chamber.

The quantity of conveyor air determines the heat supplied to the heat carrier by reaction of the conveyor air withl the carbon in the residue. If the air required for combustion is insufficient for carrying out the conveying of the heat carrier, other gases not participating in the reaction are preferably added, such as for example com-v buston `gases or even nitrogen. If the heat carriers removed from the overflow shall he substantially free. ofp

carbon, steam, if desired also carbon dioxide or even both,v may be mixedr additionally with the conveyor air. Any carbon of the residue which is not consumed in the heating is thereby converted into carbon monoxide and hydrogen. This is particularly advantageous if the' conveyor gases are further used after leavingl the pneumatic conveying and separation of the circulating heat carrier. The said gases may, for example, be supplied directly to a steam boiler connected in line. Secondary air is blown into the steam boiler to burn up completely the combustible components of the reaction gases and of the fine dust carried along with them. l

This method of carrying out the hereindescribed proci ess has the advantage that the supplied material to be degasified is converted completely into concentrated degasification gas, weak gas and fine dust in a highly heated form. The process `may thus advantageously be com- `bined with pulverised fuel firing installations, for example in steam boilers, for producing concentrated` degasification gas, for example for town gas purposes, and liquid hydrocarbons, and for converting the residual coke into producer gas and dust of the very finest form at a high temperature, which in this for-m may be used with great advantage for firing steam boilers.

rIhe process may, however, also be employed with great success, for example in combination with roasting and sintering furnaces or other metallurgical processes. The utilisation of the sensible and chemically combined heat of the conveyor gases `and entrained fine dust is also effected, preferably in a stearn 'boiler or the like, if the carbon of the degasification residue has not been completely gasilied, but a portion is removed as granular residue at the overliow- 1 from dust 4by separators for removal of fines for example in the form of highly effective multiclones. As a result of the line dust removal, higher gas velocities may be used in the steam boiler, or even for example in a gas turbine. The separated fine dust is then used for the heat carrier circuit or for other purposes, for example it is supplied to a separate steam boiler, a sintering apparatus or the like for utilising the carbon contained therein.

Thedegasification may be carried out according to choice at high, medium or even low temperatures. This` mainly depends upon the desired nature of the degasiiication products. if a high degasification temperature, for example ()o C. is used, the tar liberated from the degasification material is decomposed to a considerable extent and converted into gas, and the volatile constituents of the degasification material are expelled to a considerable extent. In this case, only a small quantity of coke remains as residue. lf, on the other hand, degasiflcation is carried out at low temperature, for example 600 C. the tar liberated from the degasification material is extensively preserved and leaves the degasication chamber together with lthe degasification gas. The quantity of degasilication gas is less than in the case of high tempera ture degasitication, but-in general the gas has a higher calorific Value; the quantity of the residue is also greater,- Since a portion of the Volatile constituents remains in the coke. If, when working at low temperatures, it is de sired substantially to avoid the consumption of coke for heating the heat carrier, heating gases may advantageously be added to the conveyor air for supplying the necessary quantity of heat for heating the heat carrier by combustion of the heating gases.

In some cases, it may be desirable to add Water gas to the degasitication gas, for example in order to increase the quantity of gas or also to reduce the caloric value of the' gas, so that the mixed gas satisfies, for example, the' standards for town gas. The production of water gas may `be combined with the degasificatiou, for example'by .tiva

masia-1:42.

ittoducing; steam. intorthe-lowen part of theV degasificaz-` tion chamber and allowingA itito` pass through thechan1- `bei' chargeseonsistingof. a'- mixture of fuel and circulating heat-` carrier of high temperature. The steam reacts partly with the carboniof the fuel,.and by dissociationin accordance. with the` equilibrium conditions produces mainly carbon monoxide'and hydrogen, together with certain quantities of-c-arbon dioxide; Adjustment of the caloric value of thelgas may also be effected by other means, for example by injecting together with the steam or instead of steam, air, oxygen or oxygen-enriched nir ory the. like. The-injection of` steam or the like and the production of water gas `increase thequantity ofgas passingthrough thechargc, Iso that a correspondingentraim meut of dust may be expected. Preferably, therefore,v thelwaten gaswisprodu-ced` in a. 'separate apparatus, or in an chamber connected in: series with the degasitication 'chamber andfis addedto theldegasication gas only after it 4hassbeen cleaned;

lf the.` recovery of` the tar contained in the fuel is to be: as completeV as possible', which i-s` above all attainable by using low degasiiication` temperatures and avoiding decomposition, the introduction of small quantities of scavengingggases e. g. steam or combustible gas into the degasication chamber maybe: of advantage, so that `by 'a scavenging'efect, a more rapid removal of the tar vapours is; obtained, thus preventing 'as far as possible, the decomposition of the'tar. Inv doing this, care should `be taken. to avoid as far as possible anyeddying or whirling upvof thedust.

From the point of viewof heateconomy, it is* of ad vantage to preheat the air for the pneumatic conveying ofxthe' circulating heat carrier. and/ orlthe freshly supplied fuel. It isi advantageous to utilise the heat of the degasication gas discharged in the hot condition or of the reactiongasor gases, `after the separation of the circulatingheat carrier, for heatingfthe air and/ or the fuel, in which case, the fuel mayl be previously dried and also, if necessary, its caking tendencies may be previously removed by a thermal treatment.

The" freshA material to- 'be supplied and `degasiiied is preferably: uniformly and inti-mately mixed with the heated heat carrier. Preferably, this is carried out in ani. apparatus through which the` heated heat carrier passes'ina thin stream and ata correspondingly high velocity, the fresh fuel being fed into the stream at the same time` ina. uniform` and steady manner: For example, about three to twenty times, and preferably by nine to twelve times the quantity by weight of heat 4carrier tofresli` material is employedrelatively` to thequantity of freshV fuel,.so that the individual fuel grains are well enveloped and rapidly heated. ln consequence of the fuellbeing made .lean by the circulating heat carrier, the rapidi movement at the inlet-to the degasication cham- Iberfandthe rapid heating, there isno -appreciablecaking together or` evenlump formation in the case ofcaking fuels, so that'allfuels `may be used, irrespective of their caking tendencies. Any caking togetherv of a few in-V dividual grainsis-harmless and is, for the greater part, destroyed inthe pneumatic conveyorlduct.

` Preferably, the process ofthe present invention iscara ri'ed outin an' apparatus inwhich the separating chamber forA the heated heat carrierA is situated above a degasification chamberand is `connected'to"the'latter by a prefer--y ablynarrow shaft forthe supply of' the heated heat carrier. The conveying path for pneumatic conveyingis preferably situated in the interior of the apparatus so that it passes through the degasication chamber, the supply channel for the mixtureoffheat carrier: and material toybee degasitied and .theseparatingschamberfor the heat' carrier. It. is.ho.weyer;. also, possible toarrange the conveying path outside the degasication apparatus.

In order to enable the invention to be more readily understood, reference is made to the accompanying drawingwhchi illustrates diagrammatically and by wayvolf?` eilte-` ample, one embodiment of apparatussuitable for carrying@ the hereindescribed process into practical eiect.

Fig. l is a vertical section through`l such anlapparatus Fig. 2 shows some details'of this apparatus.

in said drawing, 1 denotes a verticalv rectangular orl round shaft in which degasification iscarriedout.` 2 is`a` pneumatic conveying channel, in which the heat carrier is elevated while being` simultaneously heated. 3` isithet primary separator for separating the heated heat carrier! from the gases, and is shown in the form of. a settling; chamber. apparatus and 1S is` a refractory lining.` The. separator 3f is situated above the degasification chamber 1f and iscoti-A nected to said chamber 1 by a narrow channel 4in whichthe heat carrier, heated to a temperature ofA about=1600 to C., for example 1000" C., accordingftorequire ments, continuously descends into the chamber 1. The# channel 4 is shown as an annular space aroundltheiconf veyor section 2 which passes axially through the deg'asi cation chamber l. The channel 4 may alsobei formeel?V as an enclosed channel, independent of. the conveyingI channel 2.

The fresh'fuel is fed continuously into` the channel"4 from a supply container 5. The feedingdeviceinithe'f Vey the charge introduced into the casing 2li by the supply `line 22 and carried by the annular disk` 24into theliolesor slots 7 through which the charge gets into thechannel" 4. The shovels 2S are arranged in the casing 21, the? holes or slots 7 along the wall of theK channel, botlrva-tL suitable, advantageously equal spaces.

The fuel, mixed with the hot heat carrier, rapidly des` scending through the channel 4 into the degasication-'t chamber and being heated gives oi its volatilefcoustits4 uents which ascend in the gas-collecting space 8ar1dwatf- 9 pass from the degasiiication chamber, for examples-tol cooling, condensation and scrubbing apparatus of. knownI type not shown in the drawing. The -degasiiied fuel, in mixture with the cooled heat carrier, at a temperaturef of about 400-1000" C. for example 700 C., according; to the selected conditions, descends slowly in` chamber'll` and via a throttling device 10, which regulates` thecircu' lating quantity of heat carrier, passes laterally in'to'the lower part of the conveying channel 2. Airlis introduced from below into the conveying channel2'via1the`duct`1`1, said air being advantageously heated in a'superheater` 12 to a temperature of about 200 to 1000* C. for examplef 500 C. The heat exchange may be carried out with'they hot degasification gas or the hot combustible gases'ofY the conveyor air or also With any desired extraneous source of heat. The conveyor air supplied takes the heat? carrier upward in the conveying channel 2 and reacts with the carbon in the heat carrier, .with the formation* of carbon dioxide and carbon monoxide anda correspond-fl ing evolution of heat, so that the heat carrier is heated tof the desired temperature between about 600 and 12009 C., for example to l000 C. fu the separator 3 the coarser" grains of the heat carrier are separatedlfrom the reactionf gases and returned to the Idegasiiication chamber 1, thus* closing the circuit of the circulatingheat carrier. The-f reaction gases, still charged with the nergrains of' dust,l leave the separator 3 at 13 and are suppliedtoa steam?. boiler 1d, in which the reaction gases and dilsta're'com.` pletely burned with the addition of air(fromthe`d'ot 15"). Connect-ed to the channel 4 or separator 3, at a point above the feeding device d, 7 for the fuel, is an overow duct 16, through which excess of heat carrier, for example.`

17 is a sheet-metal casing; surrounding-tha cokeg'is removed from the cycle. In order to ensure satisfactory operation, it is necessary that at least small quantitiesv should be continuously withdrawn from the overflow conduit 16, this being preferably controlled. Withdrawal of heat carrier at the overflow ensures that the channel 4 is continuously filled with heat carrier or fuel, this being necessary in order to obtain a reliable gas seal between the degasilication chamber 1 and separator 3, in combination with a suitable pressure regulation in the degasification chamber 1 and the separator 3 in mutual dependence. If the fuel does not form an excess of coke which can be withdrawn from the overflow duct 16, an additional heat carrier is advantageously supplied to the cycle in order to ensure the existence of a'closed charge. The heat carrier withdrawn from the overflow conduit 16 may then be returned to the cycle, for example together with the material to be degasitie'd. 1,9 is a grate arranged in the lower part of the degasiti cation chamber 1, to which steam may be supplied through the pipe line 20 for effecting the formation of water gas in the degasification chamber, or to scavenge the cham.- ber so that degasification gas charged with tar vapours will be withdrawn more rapidly from the chamber.

J By means of the aforedescribed apparatus, it is possible to carry out the degasication of finely granular or pulverulent fuels.

' The process and apparatus of the present invention arc particularly adapted for the production of gas of high calorilic value, for example, for town gas purposes, or for the recovery of individual gaseous hydrocarbons from the gas or for the recovery of tar in combination with power generation, for which the reaction gases formed withthe conveyor air and the line dust at a high temperature are used with particular advantage. Due to the simplicity of construction and the rapid readiness for operation of the apparatus, the process is to be used with particular advantage for covering peak require ments. For covering special peaks in gas and power requirements, which. occur at different times, it is possible preferably to use the tar produced, in addition to adjustment of the working conditions adapted to the necessary requirements. By returning the tarto the degasication chamber and decomposing it, the gas yield may be increased, or the tar may be burned, for example in a steam boiler.

. The apparatus is of closed construction and may also be operated at higher pressures, if this should prove desirable in special cases, for example for the better utilisation of hot conveyor gases produced under pressure, for example in gas turbines, or for the production of degasification gas under super-atmospheric pressure, which facilitates cleaning and transport.

What we claim is:

- 1. In a method for the degasication of normally solid nely. divided fuels, the improvement which comprises mixing a heated solid and solid fuel together', said solid being heated to at least the degasification temperature of said fuel, moving the mixture downwardly through a confined `feed column, into a closed degasilication zone, establishing a free surface of material in the closed degasication zone, Amoving the mixture downwardly in a non-uidized bed through said degasification zone, sealing the material feed and discharge from said Zone against the passage of gas, removing the solid and fuel residue from the bottom of said zone, removing gas produced from the free surface, elevating solid residue material in. a confined zone with a combustion supporting gas, burning a portion of said residue material in said elevating zone, separating the coarse heated solid from the gas and fine material, and returning the coarse heated solid to said mixing step.

v2..,The improvement according to claim 1 in which maintain for said coarse solid return Va ratio 'of returned solid to fuel of about 3-20:1 by weight, and in which saidA sealing is accomplished by columns of said residue material.

3. The improvement according to claim 2 in which said returned solid is heated to a temperature of at least- 600-l200 C.

4. The improvement according to claim 3 in which said fuel is coal, in which said combustible solid is ma terial derived by the gasification of such coal and in which said mixture is gravitationally moved throughsaid degasification zone.

5. The improvement according to claiml 4 in which the particle size of at least one of said fuel and of said solid is of the order of magnitude from 0.1-1.0 mm.

6. The improvement according to claim 41 in which said sealing is accomplishedby columns of residue material of lesser cross-sectional area than that of the mixture passing through said degasication zone, in which said mixture is gravitationally passed through said degasitication zone, and in which said fuel is fed to said mixing step to maintain for said coarse. solid return a ratio of returned solid to fuel of about 3-20:1 by weight.

7. The improvement according to claim 6 in which said fuel is coal, in which said combustible solidisde` rived by the degasitication of such coal, and in which the particle size of at least one of said coal and said degasified coal is within the order of magnitude not to ex ceed about 1.0 mm.

8. The improvement according to claim 7 in which" said combustible solid is heated to at least a temperature 0f 600-l200 C. v

9. The improvement according to claim 6 in which said residue material is elevated in a confined zone passing substantially centrally through said mixture and through said sealing columns.

10. The improvement according to claim 1 in which said fuel is fed to said mixing step to maintain for said coarse solid return a ratio of returned solid to fuel of about 3-2011 by weight.

11. The improvement according to claim` 1 in which said sealing is accomplished by columns of said residue material.

References Cited in the file of this patent UNITED STATES PATENTS 1,899,887 Thiele Feb. 28, 1933 1,977,684 Lucke Oct. 23, 1934 2,376,564 Upham et al May 22, 1945 2,445,327 Keith July 20, 1948 2,446,221 Ferguson Aug. 3, 1948 2,461,021 Atwell Feb.l 28, 1949 2,480,670 Peck Aug. 30, 1949 2,519,340 Bailey Aug. 22, 1950 2,527,197 Rollman Oct. 24, 1950 2,527,198 Rollman Oct. 24, 1950 2,579,397 Roetheli Dec. 18, 1951 2,582,710 Martin Jan. 15,'1952 2,582,711 Nelson Ian. 15,1952 2,606,144 Leder Aug. 5, 1952 2,609,332 Bowles Sept. 2, 1952 2,618,544 Fischer Nov. 18, 1952 2,639,263 Lelfer May 19, 1953 2,627,499 Krebs Feb. 3, 1953 FOREIGN PATENTS 189,542V Great Britain Feb.v 18, 1922 578,711 Great Britain Iuly 9, 1946 582,055 Great Britain Nov. l4, 1946 

1. IN A METHOD FOR THE DEGASIFICATION OF NORMALLY SOLID FINELY DIVIDED FUELS, THE IMPROVEMENT WHICH COMPRISES MIXING A HEATED SOLID AND SOLID FUEL TOGETHER, SAID SOLID BEING HEATED TO AT LEAST THE DEGASIFICATION TEMEPRATURE OF SAID FUEL, MOVING THE MIXTURE DOWNWARDLY THROUGH A CONFINED FEED COLUMN, INTO A CLOSED DEGASIFICATION ZONE, ESTABLISHING A FREE SURFACE OF MATERIAL IN THE CLOSED DEGASIFICATION ZONE, MOVING THE MIXTURE DOWNWARDLY IN A NON-FLUIDIZED BED THROUGH SAID DEGASIFICATION ZONE, SEALING THE MATERIAL FEED AND DISCHARGE FROM SAID ZONE AGAINST THE PASSAGE OF GAS, REMOVING THE SOLID AND FUEL RESIDUE FROM THE BOTTOM OF SAID ZONE, REMOVING GAS PRODUCED FROM THE FREE SURFACE, ELEVATING SOLID RESIDUE MATERIAL IN A CONFINED ZONE WITH A COMBUSTION SUPPORTING GAS, BURNING A PORTION OF SAID RESIDUE MATERIAL IN SAID ELEVATING ZONE, SEPARATING THE COARSE HEATED SOLID FROM THE GAS AND FINE MATERIAL, AND RETURNING THE COARSE HEATED SOLID TO SAID MIXING STEP. 